Metal core PCB cooling is broadly classified into two types – Passive and Active.

When the ambient temperature is lower than the operating temperature of the PCB, passive cooling methods can be used to dissipate heat from the components and board. Under this condition, the thermal gradient between the PCB and the ambient will be large, thus forcing larger heat flux away from the components and board itself.

Passive cooling uses natural convection to release heat such as a thermal pad or thermal paste . A thermal pad is usually placed beneath an active component to allow heat to be dissipated to the nearby ground plane or conducted to the bottom of the Metal core PCB through stitching vias (thermal vias). A heat sink can be added to the ground place to dissipate more heat if a single thermal pad is insufficient to bring down the temperature to the required level. To increase the heat flux into heat sink, the PCB designer can also use the heat sink with a thermal pad/ thermal paste.

Evaporative cooling is another passive method used to cool active components that generate a significant amount of heat. However, if the evaporative cooling system accidentally leaks or ruptures, it will result in fluid leaking all over the board. Hence, this method is not ideal.

The active cooling method relies on external devices to enable heat removal. This method is used when the passive cooling does not cut it.

Most often a fan is used in active cooling. The fan helps to provide better cooling for the active components like FPGAs, CPUs, or other devices with high switching speeds. Fans are noisy due to PWM signals, also AC-driven fans with an electronic switching control will become the cause for radiated EMI. Hence, if a fan is used, nearby traces components should have enough noise rejection/immunity or even shieling in extreme cases.